Image size report
What shrinking images would save
Photographs uploaded straight off a phone or a camera are usually several times larger than anything they are used for. This finds those images, works out what each one would save at a sensible size, and leaves the decision to you. It changes nothing.
What it tells you
- Which images are worth shrinking, and what each would save in kilobytes and as a percentage.
- The saving on the current version of each file, and separately how much its older versions hold, which is usually where the real weight is.
- The proposed dimensions, so you can confirm nothing gets mangled.
- Why every other image was left out, listed rather than silently dropped.
- Where the file type does not match its extension, which is worth knowing on its own.
How it runs
- Sign in and pick a scope. Clicking the tile asks which account to use and how to connect, signs you in if you are not already, and drops you straight on the site list. No feature page asks you to connect a second time. Sites, libraries or folders.
- It measures, largest first. The largest candidates are downloaded and re-encoded in memory to find the true saving, up to a download budget (25 GB by default). The rest are estimated, and the How it was worked out column says which is which.
- Save the workbook. Summary, Candidates and Skipped. The workbook is also the file you mark up: set Action to Reduce or Skip on the Candidates sheet.
- Approve, then apply separately. Mark the images you want reduced and run Reduce image sizes from Optimise Storage Tools. Aspect ratio is never changed, only scale.
How it works
A ticked site includes its libraries and its subsites. Libraries are read one at a time, hidden ones left out unless you include them, and the Forms folder is ignored. It looks at JPEG, PNG, GIF, TIFF, WebP and BMP files. Animated GIFs are skipped, HEIC is not supported, BMP is considered only when converting to PNG is on, and images too large to decode safely are skipped. Files under 1 MB are counted but not considered.
Candidates are taken largest first. Each is downloaded and re-encoded in memory at your settings, which by default means quality 80 and no change to dimensions unless you set a longest edge. Measuring stops once a fixed download allowance is used up, and the remaining candidates are estimated from their size, dimensions and format; the How it was worked out column says which. An image is a candidate only when the saving reaches your minimum, 20% by default.
The saving shown for a file is worked out on its current version. The total size across all versions is shown beside it, and the bytes held in older versions are a separate line on the Summary sheet. A file whose content is not the format its extension claims is marked, and counted on Summary.
A library that fails before any file is read is listed as left alone; one that fails part-way is marked partly read and the totals become at least figures. A file that fails is counted and the run continues. The reduction run reads its decisions from the Action and Unique ID columns of the Candidates sheet, which is how a decision finds the right file even after it moves or is renamed. The workbook goes into History when the run ends.
What you get
An Excel workbook, named like contoso-image-reduction-report-20260901-142207.xlsx, kept in Report History whether or not you save it. Saving (KB) is for the current version only; Total size across versions (KB) shows what the older versions hold. The Unique ID column is how your marked-up workbook is matched back to the right file even if it moves or is renamed.
Summary sheet
Scope, totals, how the numbers were worked out, and what the run would save overall.
Candidates sheet
Images worth reducing, with the saving.
| Column | Example |
|---|---|
| File Name | site-visit-0431.jpg |
| Original KB | 6,412 |
| Reduced KB | 742 |
| New dimensions | 2000 x 1333 |
| Versions | 3 |
| Total size across versions (KB) | 19,236 |
| Saving (KB) | 5,670 |
| Saving % | 88% |
| How it was worked out | Measured |
| Action | Reduce |
Skipped sheet
Every image left out, and the reason.
| Column | Example |
|---|---|
| File Name | logo.png |
| Format | PNG |
| Size (KB) | 24 |
| Reason | Reducing it would not save enough to be worth replacing the file. |
What you need
- Read access to the libraries in scope. The report only reads.
What it will not do
- Measuring means downloading images, so a large scope costs time and bandwidth, up to the download budget. Figures past the budget are estimates.
- It changes nothing. Applying the reductions is a separate run against your marked-up workbook.
- Images are only ever scaled down proportionally. Aspect ratio is never altered.